Perforating apparatus



March 20, 1962 M. P. LEBOURG ETAL 3,025,794

PERFORATING APPARATUS Filed May 15, 1957 FIG.2

INVENTORS MAURICE P. LEBOURG HERBERT C. FAGAN BY W 3,025,794 PEMQRA'HNGAPPARATUS Maurice P. Lehourg and Herbert (J. Fagan, Houston,

Tex., assignors to chlumberger Well Surveying Corporation, Houston, Tex,a corporation of Texas Filed May 15, E57, Ser. No. 659,241 6 Claims.(Cl. 1tl224-) This invention relates to perforating apparatus and, moreparticularly, pertains to new and improved perforating apparatusemploying shaped explosive charges.

Shaped or hollow charges are widely and effectively used as cutting orperforating devices in many welllsnown applications. Usually, a shapedcharge intended for such purposes comprises a block or a cylinder ofexplosive material into the front face of which a conical recess isformed. The recess is fitted with a suitable liner so that upondetonation of the explosive material, the explosive forces travelling inthe direction of the liner transform part of the liner material into ahigh velocity jet along the axis of the recess. In practice, this jet iscapable of penetrating many inches of steel, for example. However, inaddition to the high velocity jet, a so-called slug of liner material isformed which follows the path of the jet but travels at 'a substantiallylower velocity. It has been found that such slugs tend to plug the holeor perforation made by the jet. For example, in well casing perforatingoperations with shaped chm'ges employed heretofore, some of theperforations made by the charges may be clogged by the slugs, thuscausing a reduction in the beneficial effect of the deep penetrationsproduced by the high velocity jets.

With a view to obviating this disadvantage, it has been proposed toreplace the usual form of liner made, for example, of copper, with acopper liner to which a layer of zinc is intimately connected.Experience has shown that with such a bi-metallic liner a perforation isobtained which is as good and as deep as that obtained with an ordinarycopper liner, but the slug heretofore obtained is minimized in size ifnot altogether eliminated. It is thought that since the copper linerportion has a relatively high vaporization point a typical, highlypenetrative jet may be formed while the zinc which is readilyvaporizable cannot form a low velocity slug which undesirably plugs theperforation made by the high speed jet. Thus, bi-metallic liners havefound ready acceptance in the shaped charge art.

It is an object of the present invention to provide new and improvedperforating apparatus employing a shaped charge having a bi-metallicliner which may be fabricated more easily than heretofore possible.

Another object of the present invention is to provide a new and improvedbi-Inetallic liner for a shaped charge featuring all the beneficialresults attained heretofore with such a liner, but requiring noadherence between the elements of the liner.

Still another object of the present invention is to provide a new andimproved method for fabricating bimetallic shaped charge liners.

In accordance with the present invention, a liner for the forwardhollowed-out portion of a shaped explosive charge comprises a firstelement disposed adjacent the surface of the hollowed-out portion and asecond element unadherently superimposed on the first element. One ofthe elements is made of a relatively dense and releatively ductilematerial and the other element is made of a relatively light,vaporizable material. Means are provided for maintaining the first andsecond elements in substantially fixed spatial relation.

According to another aspect of the present invention, to fabricate aliner of the foregoing type, at least one of BfiZEJh i Patented 2Q, 1952the elements is made of a malleable or ductile material and the elementsare formed by means of one or more die-stages. At some point in thefabrication of the shaped explosive charge, the elements are compressedtogether so as to deform at least one and bring adjacent surfaces intorelatively close contact. For example, this may occur in one of thedie-stages. Thereafter, the elements are mechanically locked together infixed spatial relation.

Alternatively, the elements may be formed separately, for example, bypassing a material for each through a common set of die-stages.Thereafter, they are superimposed and forced into an explosive materialfor the shaped charge thereby to pack the explosive "and deform at leastone to bring adjacent surfaces of the liner elements into close contact.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation, together with further objectsand advantages thereof, may best be understood by reference to thefollowing description taken in connection with the accompanying drawingin which:

FIG. 1 is a view in longitudinal cross section of one form of shapedexplosive charge perforating apparatus embodying a bi-metallic linerconstructed in accordance with the invention; and

FIG. 2 is a view similar to the one shown in FIG. 1, but illustrating analternative embodiment of the invention.

In FIG. 1 of the drawing, there is shown a shaped ex plosive chargecomprising a hollow container 10 of generally conical form receiving inclose interfitting relation an explosive charge 11. The container may beconstructed of any material of sufiicient strength to act as a retainerof the explosive material. For example, it may be fabricated of a heavyor dense material, such as lead or steel, properly shaped to minimizethe effects of undirected pressure waves while increasing thepenetration power of the device for a given amount of explosive charge.

The charge 11 is formed with a hollowed-out or conically shaped forwardend 12 which receives a closely fitting conical liner 13 constructed inaccordance with the present invention. Liner 13 is comprised of a firstelement 14 of generally conical form disposed adjacent and ininterfitting relation to the surface of hollowed-out portion 12. Element14 is made of a relatively dense and relatively ductile material, suchas copper or soft iron. Liner 13 further comprises a second element 15of generally conical form interposed between elements 14 and portion 12of charge 11. Element i5 is made of a relatively light, vaporizablematerial such as zinc or aluminum and is unadherently superimposed onelement 14-, in intimate contact therewith.

To maintain elements 14 and 15 in fixed spatial relation housing 10 isprovided with an inwardly deformed, annular ridge 16 which engages thebase ends 17 and 18 of the liner elements. Thus, element 14 ismaintained in engagement with element 15 which, in turn, is maintainedin engagement with the surface of hollowed-out portion 12 of explosive11.

The shaped charge thus-far described may be detonated in a suitablemanner, as by a Primacord 19 disposed at the rear end of explosivecharge 11 and adapted to be detousted by an electric blasting cap (notshown). Where, for example, the charge is employed in well perforatingoperations, it is suitably supported in a housing or carrier adapted tobe lowered into a well (not shown) and the blasting cap is ignited by anoperator from the surface of the earth.

In operation, Primacord 19 is detonated and it, in turn,

detonates the rear end of explosive charge 11. Thus, an explosive frontis generated which creates a stream of flowing metal from liner 13comprised mainly of the copper material in element 14. This streamextends outwardly rom explosive charge 11 to form a high speed jetcapable of producing deep penetrations in a target material.

During the collapse of liner 13 wherein a portion thereof constitutesthe perforating jet, any slug which might have been formed by materialin the position occupied by element 15 cannot be formed because element15 is Vaporized at the temperatures produced during the formation of theperforating jet. Heretofore, it was thought that elements 14 and 15should be bonded together or otherwise adhered to one another to preventdistortion of the jet formation stream resulting in an undesirable lossof penetration power. ,7 Comparative tests have shown, however, that ashaped charge provided with a liner embodying the present invention isentirely satisfactory and as efficient as a charge having bonded linerelements. This analysis is presented merely as an aid to anunderstanding of the utility of the invention, but should not beconsidered as restrictive or in any way limiting the scope of theinvention.

Since the elements 14 and 15 need not be adhered to one anotherthroughout their adjacent surfaces, a shaped charge liner embodying thepresent invention may be conveniently and easily constructed. Forexample, the elements is and 15 may be formed by a conventional andrelatively inexpensive die stamping process using malleable or ductilematerials. Thus, fiat strips of copper and Zinc stock may be placed inface-to-face relation and run through a set of dies which progressivelyform the desired conical form. In this way these elements are in closeor intimate contact and there is requirement for adherence or cohesiontherebetween. Of course, they are physically maintained in place bymeans of annular ridge 16 of housing 10.

Instead of forming the elements 14 and 15 together, they may be stampedseparately, preferably by means of the same set of die-stages, and thensuperimposed to constitute liner 13. Thereafter, explosive 11 is loadedinto container and the liner 13 is forced into the explosive with aforce on the order of 20,000 pounds. This, of course, forms thehollowed-out section 12 in the explosive, packs the explosive to adesired density, and deforms either or both of elements 14- and to bringtheir adjacent surfaces into intimate, but non-adherent, contact.Mechanical locking of the elements may then be effected.

It is thus evident that elements 14 and 15 may be brought into closeassociation by exerting a force sulficient to deform one or both ofthem. Accordingly, either or both of the elements should be malleable orductile so as to permit this deformation. Moreover, the deforming forcemay be applied at some Stage of the fabrication to the shaped explosivecharge, that is, this may occur during the formation of the liner or atthe time the liner is pressed into the explosive material of the charge.

in the modified arrangement illustrated in FIG. 2, components which havetheir counterparts in FIG. 1 are represented by the same referencenumerals. Here, a modified liner 13' is comprised of a relatively denseconical liner element Li made, for example, of copper disposed ininterfitting relation within a liner element 15' composed of arelatively light, vaporizable material, such as zinc. As in thearrangement of FIG. 1, elements Idand 15' are unadherently superimposed,however, to maintain them in fixed spatial relation element 14 isslightly shorter than element 15' and the latter is crimped or inwardlydeformed to provide an annular ridge which engages the base end 17 ofelement 14.

To construct liner 13 flat copper and Zinc stocks are run togetherthrough a number of progressive die stages on a conventional stampingmachine. Each successive die operation forms a piece of the compositematerial into a shape more closely approaching that of a cone. The finalstage produces a cone which is then trnnrned at the base by means, forexample, of an appropriate set of dies.

The same or another set of dies may be arranged to undercut element 14,and in a further step, element 15 is crimped over the edge 17 of element14 thereby to lock the elements together. If desired, this last set ofdies may be appropriately arranged to effect the final trimming ofelement 15, although this operation may take place during a precedingstage.

From the foregoing discussion it is evident that although the elementsof liner 13 or 13 are not adherent to one another, the effectiveness ofa shaped explosive charge embodying the present liner performsefiiciently and eflectively. Furthermore, the liner can be fabricated bymeans of simple stamping operations and is thus considerably lessexpensive to construct than heretofore possible.

Obviously, other arrangements may be employed for mechanically locking,the elements of the liner together. a

For example, the inner element may be provided with a series of openingsannularly spaced about its base and the outer element may be,appropriately deformed so as to enter these openings thereby locking theelements together. Alternatively, the elements may be joined together attheir base ends by one or more solder points or they may be spot weldedtogether at a number of points.

In constructing a bi-metallic liner according to the present inventionfor a specific practical application, two

sheets of metal each 0.012" thick were run simultaneously through a setof die-stages. One was composed of 99% pure copper, fully annealed,while the other was composed of an alloy known as deep drawing zinccontaining lead in about 0.08%. The sets of dies were constructed ofchrome-plated hard steel and a thrust of 5,625 lbs. was employed. Thedies were appropriately lubricated to prevent scoring or galling of thezinc. The resulting conical liner had a base diameter of 1 7 and aheight of l% and a wall thickness of 0.024" at the base end and 0.027near the apex end. The liner Was forced into a powder charge of 15 gramsto complete a shaped explosive charge. Of course, the foregoing ispresently only by way of example and should not be considered in any wayas limiting the scope of the invention. For example, other thicknessesof the metals and/ or other amounts of thrust may be employed. Moreover,by means of dies of appropriate size, liners of any desired dimensionsand shape may be produced.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects, andtherefore the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

We claim:

1. A shaped charge device comprising a shaped explosive charge having acavity at the forward end thereof, and a layered structure having thesame shape as the surface of the charge cavity and including a firstouter layer of material which is in contact with the explosive chargewhen the liner is placed within the cavity and a second inner layer innonadherent intimate contact with the outer layer along the innersurface thereof, the inner layer being made of a relatively dense andductile material, having a relatively high vaporization point so as toform a high velocity perforating jet of the material when the charge isdetonated and the outer layer being made of a relatively light materialhaving a relatively low vaporization point such that it tends tovaporize upon detonation of the charge, thereby inhibiting the formationof a low velocity slug.

2. A shaped charge device according to claim 1 Wherein the layeredstructure has a conical shape.

3. A shaped charge device according to claim 1 wherein the outer layeris made of zinc and the inner layer is made of copper.

4. A shaped charge device according to'claim 1 wherein each layer of thestructure comprises a sheet of material formed in the shape of thecharge cavity surface.

5. A shaped charge device according to claim 1 wherein the outer layerof material includes an inwardly projecting portion adapted to engagethe inner layer and retain it in intimate contact with the outer layer.

6. A shaped charge comprising a generally cylindrical housing having anopen end portion, a charge of explosive material within the housingformed with a cavity directed inwardly from the open end of the housing,and a liner for the charge comprising a layered structure Within thecavity having the same shape as the surface of the charge cavity andhaving an edge portion engaging the inside surface of the housing aboutthe periphery of the cavity including a first outer layer of material incontact with the explosive 'material at the surface of the cavity, and asecond inner layer in nonadherent intimate contact With the outer layeralong the inner surface thereof, the inner layer being made of arelatively dense and ductile material having a relatively highvaporization point so as to form a high velocity perforating jet of thematerial when the charge is detonated and the outer layer being made ofa relatively light material having a relatively low vaporization pointsuch that it tends to vaporize upon detonation of the charge, therebyinhibiting the formation of a low velocity slug.

References Cited in the file of this patent OTHER REFERENCES AmericanInstitute of Mining and Metallurgical Engineers, Technical PublicationNo. 2158, class A, Mining Technology, 1947.

